The 'current' SDK determines what is in any new *.bin files you generate. When you switch back to an old version of cgminer you are using the old *.bin generated with an old SDK unless you delete them.
I think kano is right. At least it was the reason preventing me from updating from version 2.1.2 since phatk opencl code has changed and cgminer had to recompile (or whatever it does with .bin files) it.